1. Field of Invention
The present invention relates to systems and processes for honing substrates to obtain desired substrate surface roughness, and honed substrates produced thereby, such as electrophotographic imaging members.
2. Description of Related Art
There are several known methods for processing substrates to obtain a desired substrate surface roughness. Although many of these known methods are effective, many of them are uneconomical or ineffective in certain applications.
Generally, manufacturers strive to produce a substrate surface roughness that is tailored for a specific application. For instance, when preparing the surface of a substrate prior to coating the substrate with organic materials to produce an organic photoreceptor, manufacturers of electrophotographic imaging systems often roughen the surface of the substrate so that it is less reflective. A non-reflective substrate surface is beneficial in electrophotographic imaging because it minimizes an imaging defect known as xe2x80x9cplywoodingxe2x80x9d, which is caused by light interference patterns commonly associated with relatively smooth, reflective substrate surfaces.
Anodization is one method manufacturers have used to minimize substrate surface reflectance. Unfortunately, although anodization reduces plywooding, it does not eliminate the problem entirely. Another method used by manufacturers to minimize plywood image defects is rough lathing. However, like anodization, rough lathing does not entirely eliminate plywooding problems, and it is only marginally successful in specific applications.
Substrate honing is another common substrate surface treatment for minimizing surface reflectance. Conventional substrate honing processes use abrasive media to roughen a substrate""s surface to eliminate the interference patterns that cause plywooding defects. Often, high pressure air is used to propel a slurry of silica and water against the substrate surface. Typically, the substrate is submerged in a slurry bath and is positioned to ensure surface roughness uniformity. Although conventional honing is effective, it is a relatively costly process.
Because conventional honing systems require high-pressure air to blast the substrate surface with abrasive media, these systems require several high cost components including high powered pumps, specialized valves and extensive support facilities to monitor and maintain process conditions. In addition to the relatively high equipment cost, system maintenance can also be costly. Moreover, because of the large size of the equipment used for high pressure honing, conventional honing systems typically occupy a fairly large amount of floor space.
The present invention provides an economical alternative to conventional honing and surface roughening systems. The honing system of the present invention uses sonic waves to propel abrasive media against a substrate""s surface to achieve a desired substrate surface roughness. By controlling system variables including, for example, sonic frequency, system temperature, sonic amplitude and the type of abrasive media used, operators can use the present system to effectively modify substrate surface roughness.
The present invention also provides an improved honing method, and materials produced thereby. The methods and systems of the present invention are particularly suitable for honing a variety of substrates, such as substrates useful for fabricating electrophotographic imaging members.
The present invention offers several advantages over conventional honing systems. First, because the present invention uses smaller and less complex equipment, it is less expensive than conventional honing systems and occupies less floor space. Another advantage of the present invention is that it can perform substrate surface honing using reduced media velocities. By reducing the average velocity of the abrasive media, the present invention produces less energetic collisions between the abrasive media and the substrate, and thereby reduces the incidence of media inclusions and fracturing. By reducing media inclusions and fracturing, the present invention can extend the life of the abrasive media and can simplify post-process clean-up. Moreover, because the present invention experiences less equipment wear and can keep media suspended more easily than conventional honing systems, the present invention also allows users to select from a larger variety of abrasive media. The present invention also provides users with more process variables that they can adjust during processing to produce a specific substrate surface roughness. Also, because the present invention does not require a high pressure air stream to direct the abrasive media against the substrate""s surface during processing, the present invention does not suffer from the top to bottom pressure variations and related surface uniformity problems commonly associated with conventional high pressure honing processes. Finally, because the present invention uses a less complex sonic propulsion system, the present invention does not require the extensive support facilities that are necessary in conventional high pressure honing to monitor and maintain process conditions.